Electrical heating apparatus



May 29, 1928. 1,671,300

A. s. MACDONALD ET AL ELECTRICAL HEATING APPARATUS Filed May 17, 1925 2 Sheets-Sheet l MyZW BY 7 A TTORNE Y5 May 29, 1928. 1,671,300

A. s. MACDONALD ET AL ELECTRICAL HEATING APPARATUS Filed May 17, 1923 2 Sheets-Sheet 2 yn/ 33 IN VEN TOR $7M BY ac M Z A TTORNEY Patented May 29, 1928.

NITED STATES Angus s. aracnonarp, OF GREAT NECK,

. v ELLE PARK, NEW JERSEY, ASSIGNOBS To SNEAD is new JERSEY, A CORPORATION or new JERSEY."

PATENT oFFIcE.

ELECTRICAL HEATING APPARATUS.

Application filed May 17,

ratus'know'n to us for the purposes of the invention.

In the drawings, Fig. 1 is a somewhat diagrammatic side view of one form of heating" apparatus, with a wiring diagram of electrical connections. I

Fig. 2 is a fragmentary mid-sectional view, illustrating the provision of a positive'mechanical'feed for passing articles through the apparatus. "Fig; 3 is a'view similar to 1, illustrating an apparatus with a thermostatic control member separate from the heating tube.

Fig. 4 is a view similar to Fig. 1, illustrating an apparatus in which the principal features ofF igs. 1 and 3 are con ibined,

Figs. 5 and 6 are fragmentary diagrammatic' vinld-sectional views, illustrating various arrangements for positively feeding objects through a heating tube.

In the apparatus shown in Fig. 1, there is a tubular heating element 10 to receive and contain the articles to be treated. This heating element 10 may preferably be vmade of" metal tubing of suitable electrical resistance, which can be heated by passing electric current directly'through it. For this purpose, metal strap or ring terminals 11, 12 clamped about the ends of the metal tube 10 may be connected across the secondary of a transformer 13. As shown. the primary of this transformer 13 is adjustable or variable, and is connected across the A. C. power circuit '14. The primary circuit' connection of the transformer 13 includes a relay switch 15, whose function will presently be explained.

The apparatus of Fig. .1 is adapted for 1923. Serial No. 633,514.

continuous operation to heat small articles or objects fed or passed through it. preferably at a definite rate (or period of exposure in the tube) such as to give just the right duration of heating. Provision for thus passing objects through the tube 10 may be made by mounting it at an inclination, so that objects introduced into its higheriend in any suitable manner may slide or roll through by gravity. As shown, the tube 10 has a discharge opening 16 in its bottom (close to its lower end), whence the hot articles may drop intoany appropriate receptacle, such as a box, a pan of sawdust or shavings, or a quenching or tempering bath of water or 011. As one means of regulating and varying the time of passage of articles through the tube 10, its inclination may be adjusted: as shown, it is provided with a swivel or pivoted clamp mounting 17 (located aboutat its middle) for this purpose. 1

As shown in Fig. 1, one of the end clamps on the tube 10 (in the present instance, the right-hand clamp 12) has a lug which is pivoted at 19 to the lower end of an arm 20 itself pivotally mounted or fulcrumed at 21. This arm 20 has an index 22 that cooperates with a suitably graduated scale-arc 23, thus affording a visible indication of the expansion of the tube 10, and hence of the tempera ture developed from time to time. The arm 20 is also adapted to cooperate with stationary contacts 2 1, 24; (that may be set at any desired point along the scale 23) to control and operate the double relay switch 15 for the heating current. For this purpose, one side of the branching relay circuit (which circuit includes or is connected to a ,source25 of current at relatively low voltage) is connected to the contacts .24, 2 1', while its other side is connected (as through flexible lead 26) to the arm 20 itself. \Vhen the tube 10 expands sufliciently for the arm 20 to make contact at 2 1, the relay will be energized to open the switch .15 and thus prevent further rise in temperature of the tube .10. NVhen the tube 10 has cooled'a-nd contracted sufficient-ly for thereceding arm 20 to make contact at 2d, the relay will be energized to reestablish the heating circuit. i'Ihis double relay arrangement has the advantage over a single-acting, self-closing re- 60 tends along below'the -tube10,.and the widetwo or three degrees.

It will be seen. therefore,that the apparatus of Fig. 1 affords ample and varied con trol or regulation for the heating operation: as to its duration, by the ad ustment of the tube slope and the expansion of the tube 10 itself; and as to the temperature developed,

by the expansion of the tube and the adjustment of the transformer primary at 13.

Thus the tube10 itself serves as a thermostatic actuating member for gauging, controlling and limiting the temperature developed; and by proper setting of the contact'Q l, the temperature can begauged and controlled exactly as desired.

The double control over the temperature afforded by the adjustment of the transformer primaryand the thermostatic action is of advantage in allowing sufficient current to be passed through the tube 10 to heat adequately a rapid and uninterrupted stream of steel balls or other articles, without danger of overheating if and after such stream is temporarily interfered with. In such a case, the thermostatic action limits the rise of temperature of the tube naturally consequent upon the cessation of the cooling "by the stream of objects to be heated, so that when objects once more begin to pass through the tube, they Wlll not be over- I heated and perhaps injured.

"passing objects therethrough in a: definite manner, as'at a uniform rate of speed. As

shown, this mechanical feed is in the nature of. an endless conveyor 30 with one run through thetube 10. In this case, the rate of. travel and duration of heating'of the objects may be controlled by suitably regulat' 'ing the speed of the conveyor 30, which is shown as driven by a variable speed electrio motor 31 connected through worm re,-

duction. gearing 32 to the shaft of one of the sprocketsor drums around which the "members or devices 34 for positively and i definitely engaging and pushing along the objects to be treated. Inthe presentinstance, thev flexible belt or chain member exended carrierfingers 34 extend up and move along through a longitudinal slot'in the bottom of the tube. "In orderto keep the active finger ends from scraping or binding on the tube wall, a subjacent supporting plate 35 may be provided for the active run of.

the flexible cable of the conveyor.

V here the apparatus is thus provide with a mechanical feed,thetube 10 may, of course, be mounted or set a substantially horizontal position "(zero slope) as shown, since gravity. neezl no longer play the same decisive part. 7

In Fig. 2,; various parts and features are marked with the same reference characters as in Figs. 1 and 4, as a means ofidispensing with merely repetitive description.

The form of apparatus shown in Fig. 3 is adapted for heating objects in batches .or charges, one batch after another. As shown, the tube 10 is loaded full from end to end, being provided with a closure 42 at the right and stoppered with a porcelain or other insulating plug ll at the left. Here the adjustable mounting 17 serves as a convenient means for turning the tube from the hori zontal operating position shown to a vertical one, to permit its contents to run outquickly at the end of the heating period. In the present instance, the tube 10 no longer serves as the sole or principal thermostatic actuating member of the temperature-gauging means 520, 23; onthe contrary, a separate member 4 1 provided for this purpose. This member 44 consists of a rod arranged centrally inside the tube 10, secured to its bottom closure 11 and projecting. out

through a hole in the plug 42 to engage the movable arm 20; If annular, like nuts or washers, tor example, the ob ects to be treated may be strung around the rod l; and

if of granular or other such form, they may be packed around it,both conditions being illustrated; However. since the'rod 4a extends through the objects in both cases, so that thefheat caches it mainly or entirely by soaking in from the hot tube wall, through. the mass of the objects, the rod will respond to the actual heatand temperature of the objects themselves under eitl1er co'ndi-.

tion. r y

As shown, the SWltCll45 in the primary heating circuit isa simple hand switch; no

contact 24 or relav circuit is provided; and

the vigilance of the operator is depended on to'malie effective the gauging of the heating by the thermostatic member a l.

In. F 3, again, var-ions parts .and 'features are marked with the same. reference characters as in Fig.=1, as a means of dispensing withmerely repetitive description.

In the apparatus of Fig. 4 (as already mentioned) are combined various features of Figs. 1 and 3. As shown, the thermostatic rod 44 is supported by slender brackets 51, from the top ofv the tube 10,, one of which (at least) is preferably insulatively mounted to obviate'heating of the rod by flow of current through it. As shown, the

Fig. 1, extending downward instead of upward; and the positions of the parts 21, 223, are correspondingly altered. The relay switch of the single-acting, Seltclosing type. with onlythe one contact 2 1 "for the arm 90, and correspondingly simpler relay circuits than in Fig. 1. The connection 56 between the rod let and the short upper end'ol the arm (forked around the trough 53) is of the pin and slot type, so as to allow ready disengagement and reengagement. The swivel-clamp mounting 17 for the tube 10 is located near its right-hand end. To the lett-hand end of the tube 10, at its bottom, is pivoted a closure plate or trap-door 57, for which a leaf spring catch 5o is mounted on the top of the tube. also, a sort of pivoted hook crank support 60 is provided for the left-hand end of the tube 10. being connected by a link 61 to one ot the movable parts of the relay switch 15 tor the heating current.

lVhen the apparatus is to be used for treat-mg a continual succession of ob ects, the door 57 is left hanging open, the hooked catch 60 is out of action, the tube 10 is set,

at the desired inclination, as in Fig. 1; and the arm 20 functions in the same manner as in Fig. 1, under actuation by the rod ia as in Fig. 8,-the articles discharged from the open left-hand end of the tube 10 dropping intoa receptacle 63 that may contain sawdust, shavings, or a quenching or tempering bath, etc. In this case, of v course, the memher 4 1- responds more to the heat radiated from the tube'than to that of the objects themselves.

On the other hand, when'the apparatus is to be used for treating objects in. successive batches, as in 3, the door 57 is closed; the tube 10 is charged full and stoppered at its other end with a porcelain plug 42; the swivel clamp l7is lett loose, so that the tube can pivot and swing thereon freely; and the latch is hooked under the left-hand end of the tube to keep it about level, as shown. \Vhen the switch 15 is operated by, the ex pansible member 44-, the catch 60 is withdrawn, and the loaded tube 10 swings downward by gravity until arrested by a butter 65.-the pin and slot connection at 56 permitting the member 44 to disengage from the arm 20 quite readily. Ordinarily, the jar as the tube It) strikes the butter will cause the door 57 to fly open and discharge the contents of the tube into the subjacent receptacle 63'; but it a more-positive and definite action is desired, a trip or cam member 66 may be arranged in the path of the catch 58 to depress it and release thedoor just about as the tube strikes the butter.

In Fig. 4, again, various parts and features are marked with the same reference characters as in Figs. 1 and 3, so as to dispense with repetitive description.

In such apparatus as here illustrated and described, it is generallydesirable to make the tube l0 and the tlwrmostatic member (it separate from the tube) of material unsus ceptible to ermanent alteration by the temperatures dcveloped,-such as the substantial oxidation or the high temperature growth of ordinary iron and steels. On this account, some of the well-known non-oxidizing high-resistance alloys of nickel and chromium may be used, such as nichrome. For the rod ll, especially, may sometimes be used a material like so-called stainless steel (containing about 141% chromium), which will stand heating and cooling a great many times and still exhibit the critical range movements without diminution. The thermostatic member must, of course, be proportioned and calibrated with due reference to the critical temperatures of the objects to be treated, as well as with reterence to its own.

It is, of course, to be observed that the thermostatic action in Figs. 3 and 4 is in a senseditlerential with a time-lag when the tube'ltl is packed full of objects or material to be treated. That is to say, the portion of the tube ll) to the left of the clamp 17 expands first and moves the rod 44 bodily to the left, so that in the course of a heat the arm 20 may at certain earlier stages more toward or beyond the Zero end of the scale 23.

Ultimatel gon the other hand, the heat soaks through to the rod a l and the latter expands rather rapidly and moves the arm 20 the other way the full range of its movement. In any case, however, the only practical result of the differential action is to make the scale 23 shorter than it would otherwise be.

In cases where the apparatus is used to heat. a continual stream of objects. a variation or graduation of temperature in the length ot the tube 10 may be secured by suitably varying the thickness of the tube wall. In Fig. l, the thickness increases toward the right, and the temperature, therctore, toward the left, in Fig. s, the reverse variations of thickness and temperature are illustrated. In this latter case, the greater temperature of the tube at the loading end helps to bring the objects treated up to the desired or critical temperature range more quickly. In either case, the temperature scale for the tube can be calibrated by practical methods instead of being calculated.

Figs. 5 and 6 illustrate other methods of "ectin within its end.

type,here indicated by brush i positively feeding material or through the tube 10 at a definite regular rate in order to secure a uniform and accurately determinable duration of heating. In both of these latter figures, various parts and features are marked with the same reference character as in the preceding figures, as a means of dispensing with merely repetitive description.

As shown in Fig. 5, the horizontal tube 10 is supported on one or more rolls 71 for rotation about its own longitudinal axis, and

is provided with an internal helix 72 for feeding articles along screw-conveyor Wise.

he loading end of the tube 10 has an internal annular flange 73 to prevent articles ;'fl0l11 rolling or falling out after delivery within the tube by the supply chute 55 pro- The tube is driven by a helical gearing connection 32, 7ft. Current connections may be of any suitable and con-' tact ring 76.

in Fig. 6, the tube 10 may be stationary,

,and the objects to be treated (here shown as short cylinders in form) are pushed through by areciprocatory feed device, such as a crank and pitman actuated plunger80,Whose .tliio\v iiiay preferably exceed the individual length of the ob ects.

1 described, the tube 10 is shown well thermoinsulated with a heavy layer or sheathing of some highly refractory insulating mateiial,.siicli as that known as silocel, which can be had in either brick or powder form.

ili hat we claim is:

1. Electrical heating apparatus of the character described comprising a tube for receiving objects to be treated, means for passing current through the tube to heat it and for controlling its temperature, and means controlled by the temperature developed. for additionally controlling the tepr perature of the tube.

2. Electric heat treating apparatus, comprising a tube for passage of ob ects to be treated, means for passing a heating current through the tube, means for controlling the rate at which the objects pass through the tube, and means actuated by expansion incident to heating for controlling the temperature of the tube.

articles ger 8O During the relative 3. Electrical heating apparatus ofthe character described comprising a tube for receiving objects to be treated, with means ,for passing heating current through the tube, and provision for automatically controlling the heating'of the objects including an actuating member thermostatically responsive to the temperature developed but unsusceptible to permanent alteration thereby. i

4. Electrical heating apparatus of. the

character described comprising a tube for ing a thermostatic member responsive to the heat of the objects themselves.

5. Electrical heating apparatus of the character described comprising atube for passing current through the tube to heat it,

receiving objects to be treated, means for and means for gauging the heatingincluding a longitudinal thermostatic member for cntending through the objects in the tube, so as to respond to the heat of such objects themselves.

6. Electrical heat treating apparatus comprising a receptacle for receivingobjects to he treated, means for passing a current through the wall. thereof to heat it and means actuated by expansion resulting from the heating for controlling the temperature of the receptacle.

7. Electrical heat treating apparatus comprising a receptacle for receiving objects to betreated, means for passing a heating current therethrough and means actuated by ex pansion resulting from the heating for indi cating the temperature of the receptacle.

S. Electrical heat treating apparatus comprising a receptacle for receiving objects to be treated, means for passing a heating current therethrough and a single means actuated by expansion resulting trolling the temperature of the receptacle.

Electrical heat treating apparatus comprising a receptacle for receiving objects to be treated. means for passing a heating current therethrough and means indicating expansion incident to heating the receptacle.

10. Electrical heat treating apparatus comprising a receptacle for receiving objects to be treated, means for passing aheating current therethrough and temperature controlling means actuated by expansion incident to heating the receptacle.

In testimony whereof, wehave hereunto signed our names.

ANGUS S. MACDONALD. CHARLES G.,WAITE.

from heating the receptacle for indicating and. also con- 

